The present invention is generally directed to a day-night rear view mirror for a motor vehicle. Day-night rear view assemblies are well known in the motor vehicle art. These provide rear viewing by the occupant of the motor vehicle in either high light or low light conditions. The mirror assembly is adjustable by the occupant for selectively presenting a highly light reflective surface to the viewer during periods of daylight and a relatively low reflective surface during periods of low light, or at night. The relatively low reflectivity minimizes the glare which is perceived by the eyes of the occupant of the vehicle from the headlights of a following vehicle. The headlight glare from a following vehicle is bothersome to the occupant of the lead vehicle and also creates an unsafe driving condition.
Many mirror assembly designs have been utilized to produce the day-night mirror effect. One design which has been used extensively, utilizes a mirror which has a triangular cross-section. This causes the mirror to produce two different images. Since about ten per cent of light rays normal to a glass surface are reflected by it, the image which is produced by that surface has a character which is appropriate for use as a rear view mirror for a motor vehicle at night. The remaining ninety percent of the light rays, which pass through the surface of the glass, are reflected by the silvered backing of the mirror. Since the mirror has a triangular cross-section, the rays of the image which is produced by the front surface of the glass diverge from the rays of the image which is produced by the silvered back of the glass. By the same token, images from two different points or sources of light converge to a single point, i.e. the occupant of the motor vehicle. When the mirror assembly is mounted inside a motor vehicle, the roof of the vehicle is the point source for one image. Since there is no light source in the roof of the vehicle, only one image is visible to the operator. Therefore, by adjusting the position or tilt of the mirror with respect to the operator, the operator views either an image from the light which is reflected from the surface of the glass, or an image which is produced by the light which passes through the surface of the glass and is reflected by the silvered back of the glass.
The mirror assembly which utilizes a movable triangular mirror or prism is limited to use within the vehicle. If this type of mirror is used on the exterior of the vehicle, or in a convertible with the roof down, two images are visible to the operator at the same time. For example, as the operator drives down a street which is lit by street lights with cars following behind, the image of the street light is viewed by the operator as overlapping the image, or images of car headlights which are behind the operator.
In an attempt to solve the problems described above, a day-night rear view mirror assembly has been developed which includes a transparent glass panel which is positioned in a housing between a mirror and the area to be viewed. The mirror is surrounded by a movable opaque shade having a window formed there through that may be brought into and out of registry with the light reflective surface of the mirror. When the mirror assembly is in the night viewing position, the window is out of registry with the mirror which is covered by the opaque shade material. Images such as headlights of following vehicles from the rear of the vehicle are reflected by the plain glass panel in front of the mirror. Since the light reflectivity of the plain glass panel is much lower than the light reflectivity of the mirror, the reflected image, which is viewed by the vehicle occupant, is of greatly diminished intensity. When the mirror assembly is in the daylight position, the window is in register with the mirror so that images from the rear of the vehicle pass through the transparent glass panel and are reflected by the mirror for viewing by the vehicle occupant.
Although the above described day-night rear view mirror enable the mirror to be used from a position outside of the vehicle, it has been less than satisfactory in actual practice. For example, during daytime viewing, a faint second image is perceived by the viewer which is offset from the principle image which is reflected by the mirror. This represents an annoying condition to the operator of the vehicle and tends to be distracting, which is not conducive to complete safety. These and other difficulties experienced with the prior art day-night rear view mirror assemblies have been obviated by the present invention.
It is, therefore, a principle object of the invention to provide a day-night rear view mirror assembly which is selectively actuated for providing an attenuated image for nighttime viewing and a clear, bright image during daytime viewing without any annoying double image.
Another object of this invention is the provision of a day-night rear view mirror in which both the bright, daytime image and the attenuated nighttime image are clearer than those of prior art rear view mirrors and without a double image.
A further object of the present invention is the provision of a day-night rear view mirror which is considerably simpler in construction than previous day-night mirrors and easier to use.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the Specification and covered by the claims appended hereto.